HL-2A Experiments Scenarios for 2009


In 2009 experimental campaign, with the total auxiliary heating power of 4.5MW (ECRH/2MW, NBI/1.5MW, and LHCD/1MW) and the effective SMBI technique, the physical experiment was focused on confinement improvement of HL-2A plasmas from L-mode to H-mode as well as particle transport, impurity transport, edge plasma and turbulence and MHD instability. In April, the repetitive H-mode discharges with Type-III ELM were successfully obtained for the first time in HL-2A tokamak by combining high auxiliary heating power of 1.2 MW ECRH and 0.9 MW NBI under low toroidal magnetic field. It is also the first time for domestic tokamak devices to obtain high confinement operation mode, which has marked a milestone in the history of magnetic confinement fusion experiment research in China. It indicates that great progress has been made in the scientific research on exploitation of magnetic confinement fusion energy in China, providing a platform for advanced study in SWIP. Furthermore, a number of achievements were obtained in the studies of HL-2A plasmas with high operation parameters, as summarized as follows. 

1)  Transport and edge and divertor physics: Edge transport barrier (ETB) was observed in the edge region of H-mode plasmas with Type-III ELM. Material limit in presence of ELM, ELM energy and particle transport from the confinement region to the first wall, the time scale and deposition position of ELM energy flux in the divertor region, were investigated.

2)  Turbulence and zonal flows (ZF): Peaked values of the low frequency zonal flows of 0~5 kHz and the geodesic acoustic mode (GAM) oscillations of 10 kHz were simultaneously observed in the float potential spectrum for the first time. Analysis confirmed that both ZF and GAM appear in the edge region of HL-2A plasmas. The new discovery has been published in Phys. Rev. Lett.

3)  Through a high temporal and spatial resolved fast scanning pneumatic-driven Langmuir probe system, statistical character of blob with an intermittent and coherent structure was analyzed in SOL. Probability of blob existence in both time and space was preliminarily estimated to be 18% and the particle flux brought by blob was 58% of the total particle flux.

4)  Advanced fuelling method and related physics: the key technique of high-field side SMBI injection was explored and density feedback control was carried out using SMBI. Transport study was performed with the modulated SMBI as a perturbation source. The existence of a localized particle transport barrier, which is a new finding, was confirmed in both experiment and simulation.

5)  Macroscopic magnetohydrodynamic (MHD) instability: Neoclassical tearing mode (NTM) was observed in HL-2A plasmas for the first time. Detailed analysis suggested that the non-linear growth rate of magnetic island was in agreement with the theoretical prediction. For the control of the NTM, ECCD was applied to control large sawtooth generated by energetic ions from neutral beam heating. It is a frontier topic in fusion research.

6)  Energetic particle physics: During ECRH heating, a new type of Alfven mode excited by energetic electron was observed for the first time. In NBI discharge, the low-frequency ion fishbone of 10~15 kHz as well as other important physical phenomena of energetic particles were newly found.